The present invention relates to a treatment method which makes it possible to perform the uniform treatment of a plate-shaped substrate, which has fine unevenness upon the surfaces represented for instance, a base plate for integrated circuit (IC) manufacturing use, a disc plate for image recording use, and a base plate for liquid-crystal display use when the surface treatment such as washing, etching, fat removing, resist friction or the like is applied by the use of the various kinds of liquid chemicals (hereinafter referred to as treatment liquid).
By way of example, in the following detailed description, the etching and washing of the base plate for IC manufacturing use (hereinafter referred to as Si wafer) which demands the uniformity and washing degree of the treatment particularly in these fields will be described.
The conventional etching methods of Si wafer are
The conventional etching methods of Si wafer are as follows.
1. A method of being dipped in the etching liquid (hereinafter referred to as a first method).
2. A method of jetting the etching liquid from the nozzles, rotating the Si wafer (as described within Japanese Patent Application publication (unexamined) Tokkaisho No. 53-8577, Japanese Patent Application Publication (unexamined) Tokkaisho No. 54-7874, Japanese Patent Application Publication (unexamined) Tokkaisho No. 56-27931, Japanese Patent Application Publication (unexamined) Tokkaisho No. 58-122732, Japanese Patent Application Publication (unexamined) Tokkaisho No. 58-196024, Japanese Patent Application Publication (unexamined) Tokkaisho No. 59-103344, Japanese Patent Application Publication (unexamined) Tokkaisho No. 59-204238) (hereinafter referred to as a second method).
3. A method of performing an etching method under the reduced pressure (as disclosed in the Japanese Patent Application Publication (examined) Tokkosho No. 60-7382) (hereinafter referred to as a third method).
Also, as the method of washing the Si wafer, existing circumstances are that the washing operation is performed by the joint use of auxiliary means for oscillating the Si wafer with most of the Si wafer being dipped in the washing liquid, or for applying the ultrasonic waves.
However, the conventional art has the following problems in the treatment such as washing or etching.
1. In the above-described first method, air is attached on the corner portion of the pattern or in the small indentation formed on the Si wafer surface to prevent the Si wafer from coming into contact against the treatment liquid to cause the uneven treatment.
Particularly, when the hydrophilic portion of the SiO.sub.2 film or the like, and the hydrophobic portion of Si, Si film nitride or the like are mixed on the Si wafer surface, the bubbles are likely to be attached onto the boundary line therebetween to often cause the uneven treatment.
Also, the air contained in the contact hole for wiring use or in the trench formed on the Si is not easy to eliminate, and the treatment thereof cannot be applied into the contact hole or the trench.
2. As the treatment liquid of the above-described second method has kinetic energies, the air bubbles are generally likely to be somewhat removed more than the first method. However, air-bubbles are often caused (especially when the hydrophobic portion exists therein) all thr more, because the bubbles are caused when the treatment liquid collides with the Si wafer. Also, even in the second method, the effects are hardly provided in the removing operation of the air bubbles within the contact hole or the trench to cause the uneven treatment. Furthermore, the treatment liquid is likely to be scattered in all directions to cause a problem in the operation safety. 3. As gas to be caused by the etching reaction is removed in the above-described third method, the etching chamber is normally kept under the reduced condition during the treatment of the Si wafer. However, in the treatment where the gas is not caused through the reaction as in the etching of, for example, SiO.sub.2 with fluoric acid or in the etching of Si of the Si nitride with phosphoric acid, the large air bubbles attached when the Si wafer has been dipped in the treatment liquid are inflated further by the reduced pressure to provide the sufficient buoyance so that the large bubbles are disconnected from the wafer surfaces. However, the small air bubbles cannot get sufficient buoyance for disconnection if they are inflated, and, then, they remain attached on the Si wafer surfaces as large bubbles during the pressure-decreasing time. The volume of the air bubbles is inflated unexpectedly 25.3 times as much under the decreased pressure of, for example, 30 Torr. Even the air bubbles of such size as may be neglected under the atmospheric pressure have large influences upon the uneven etching applied on the Si under the decreased pressure to deteriorate the uniformity. In addition, acid corrosion gas such as HF or the like is produced in large amount so as to normally retain the decreased pressure, which causes not only further corrosion of the pressure decreasing apparatus such as rotary pump or the like, but also shortens the service life of the pressure decreasing apparatus.